1GETRLIMIT(P) POSIX Programmer's Manual GETRLIMIT(P)
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6 getrlimit, setrlimit - control maximum resource consumption
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9 #include <sys/resource.h>
10 int getrlimit(int resource, struct rlimit *rlp);
12 int setrlimit(int resource, const struct rlimit *rlp);
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16 The getrlimit() function shall get, and the setrlimit() function shall
17 set, limits on the consumption of a variety of resources.
18 Each call to either getrlimit() or setrlimit() identifies a specific
20 resource to be operated upon as well as a resource limit. A resource
21 limit is represented by an rlimit structure. The rlim_cur member speci‐
22 fies the current or soft limit and the rlim_max member specifies the
23 maximum or hard limit. Soft limits may be changed by a process to any
24 value that is less than or equal to the hard limit. A process may
25 (irreversibly) lower its hard limit to any value that is greater than
26 or equal to the soft limit. Only a process with appropriate privileges
27 can raise a hard limit. Both hard and soft limits can be changed in a
28 single call to setrlimit() subject to the constraints described above.
29 The value RLIM_INFINITY, defined in <sys/resource.h>, shall be consid‐
31 ered to be larger than any other limit value. If a call to getrlimit()
32 returns RLIM_INFINITY for a resource, it means the implementation shall
33 not enforce limits on that resource. Specifying RLIM_INFINITY as any
34 resource limit value on a successful call to setrlimit() shall inhibit
35 enforcement of that resource limit.
36 The following resources are defined:
38 RLIMIT_CORE
40 This is the maximum size of a core file, in bytes, that may be
41 created by a process. A limit of 0 shall prevent the creation of
42 a core file. If this limit is exceeded, the writing of a core
43 file shall terminate at this size.
44 RLIMIT_CPU
46 This is the maximum amount of CPU time, in seconds, used by a
47 process. If this limit is exceeded, SIGXCPU shall be generated
48 for the process. If the process is catching or ignoring SIGXCPU,
49 or all threads belonging to that process are blocking SIGXCPU,
50 the behavior is unspecified.
51 RLIMIT_DATA
53 This is the maximum size of a process' data segment, in bytes.
54 If this limit is exceeded, the malloc() function shall fail with
55 errno set to [ENOMEM].
56 RLIMIT_FSIZE
58 This is the maximum size of a file, in bytes, that may be cre‐
59 ated by a process. If a write or truncate operation would cause
60 this limit to be exceeded, SIGXFSZ shall be generated for the
61 thread. If the thread is blocking, or the process is catching
62 or ignoring SIGXFSZ, continued attempts to increase the size of
63 a file from end-of-file to beyond the limit shall fail with
64 errno set to [EFBIG].
65 RLIMIT_NOFILE
67 This is a number one greater than the maximum value that the
68 system may assign to a newly-created descriptor. If this limit
69 is exceeded, functions that allocate a file descriptor shall
70 fail with errno set to [EMFILE]. This limit constrains the num‐
71 ber of file descriptors that a process may allocate.
72 RLIMIT_STACK
74 This is the maximum size of a process' stack, in bytes. The
75 implementation does not automatically grow the stack beyond this
76 limit. If this limit is exceeded, SIGSEGV shall be generated for
77 the thread. If the thread is blocking SIGSEGV, or the process is
78 ignoring or catching SIGSEGV and has not made arrangements to
79 use an alternate stack, the disposition of SIGSEGV shall be set
80 to SIG_DFL before it is generated.
81 RLIMIT_AS
83 This is the maximum size of a process' total available memory,
84 in bytes. If this limit is exceeded, the malloc() and mmap()
85 functions shall fail with errno set to [ENOMEM]. In addition,
86 the automatic stack growth fails with the effects outlined
87 above.
88 When using the getrlimit() function, if a resource limit can be repre‐
91 sented correctly in an object of type rlim_t, then its representation
92 is returned; otherwise, if the value of the resource limit is equal to
93 that of the corresponding saved hard limit, the value returned shall be
94 RLIM_SAVED_MAX; otherwise, the value returned shall be RLIM_SAVED_CUR.
95 When using the setrlimit() function, if the requested new limit is
97 RLIM_INFINITY, the new limit shall be "no limit''; otherwise, if the
98 requested new limit is RLIM_SAVED_MAX, the new limit shall be the cor‐
99 responding saved hard limit; otherwise, if the requested new limit is
100 RLIM_SAVED_CUR, the new limit shall be the corresponding saved soft
101 limit; otherwise, the new limit shall be the requested value. In addi‐
102 tion, if the corresponding saved limit can be represented correctly in
103 an object of type rlim_t then it shall be overwritten with the new
104 limit.
105 The result of setting a limit to RLIM_SAVED_MAX or RLIM_SAVED_CUR is
107 unspecified unless a previous call to getrlimit() returned that value
108 as the soft or hard limit for the corresponding resource limit.
109 The determination of whether a limit can be correctly represented in an
111 object of type rlim_t is implementation-defined. For example, some
112 implementations permit a limit whose value is greater than RLIM_INFIN‐
113 ITY and others do not.
114 The exec family of functions shall cause resource limits to be saved.
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118 Upon successful completion, getrlimit() and setrlimit() shall return 0.
119 Otherwise, these functions shall return -1 and set errno to indicate
120 the error.
121
123 The getrlimit() and setrlimit() functions shall fail if:
124 EINVAL An invalid resource was specified; or in a setrlimit() call, the
126 new rlim_cur exceeds the new rlim_max.
127 EPERM The limit specified to setrlimit() would have raised the maximum
129 limit value, and the calling process does not have appropriate
130 privileges.
131 The setrlimit() function may fail if:
134 EINVAL The limit specified cannot be lowered because current usage is
136 already higher than the limit.
137 The following sections are informative.
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142 None.
143
145 If a process attempts to set the hard limit or soft limit for
146 RLIMIT_NOFILE to less than the value of {_POSIX_OPEN_MAX} from <lim‐
147 its.h>, unexpected behavior may occur.
148 If a process attempts to set the hard limit or soft limit for
150 RLIMIT_NOFILE to less than the highest currently open file descriptor
151 +1, unexpected behavior may occur.
152
154 None.
155
157 None.
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160 exec() , fork() , malloc() , open() , sigaltstack() , sysconf() ,
161 ulimit() , the Base Definitions volume of IEEE Std 1003.1-2001,
162 <stropts.h>, <sys/resource.h>
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165 Portions of this text are reprinted and reproduced in electronic form
166 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
167 -- Portable Operating System Interface (POSIX), The Open Group Base
168 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
169 Electrical and Electronics Engineers, Inc and The Open Group. In the
170 event of any discrepancy between this version and the original IEEE and
171 The Open Group Standard, the original IEEE and The Open Group Standard
172 is the referee document. The original Standard can be obtained online
173 at http://www.opengroup.org/unix/online.html .
174IEEE/The Open Group 2003 GETRLIMIT(P)